rqt on MacOSX fails to start [ImportError?]

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I followed Homebrew source installation of Groovy on MacOS 10.7.5 and when i'm trying to run rqt i get the following error:

ImportError: numpy.core.multiarray failed to import
'import sitecustomize' failed; use -v for traceback
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/rosdep2/__init__.py", line 34, in <module>
    from __future__ import print_function
ImportError: No module named __future__
[rospack] Error: could not find python module 'rosdep2.rospack'. is rosdep up-to-date (at least 0.10.4)?
[librospack]: error while executing command
terminate called throwing an exceptionAbort trap: 6

What is wrong? Can you help me?